This invention relates generally to wire drawing and, more particularly, to a wire drawing operation of the type in which wire which is initially in a coil is unwound and is pulled through a drawing die in order to reduce the diameter of the wire. The wire then is supplied to a using or production machine such as a cold header which forms the wire into fasteners or the like.
Many wire drawing operations employ an in-line wire drawing machine of the type disclosed in Alcock et al U.S. Pat. No. 4,099,403. Such a machine includes a rotatable drum or capstan located between the drawing die and the production machine. The wire from the supply coil is threaded through the drawing die, is wrapped around the capstan and then is strung to the production machine.
In operation, the capstan is rotated to unwind the wire from the coil and to pull the wire through the drawing die. During such rotation, the wire is wound around the capstan. The production machine pulls the wire off of the capstan and consumes the wire at a rapid rate. The rotational speed of the capstan is matched to the demand of the production machine and, for this purpose, the capstan is rotated by a variable speed drive mechanism whose speed is trimmed in response to movement of a pivoted compensator arm which is biased into engagement with a loop of wire adjacent the capstan.
In some in-line drawing machines of the above type, the wire which leaves the capstan is guided between a pair of rotatable feed rolls. The feed rolls are used to advance the wire from the capstan toward the production machine during initial set up and prior to the time the production machine begins pulling the wire from the capstan.
When wire of relatively large diameter (e.g., 5/8" or greater) is being handled, a significant time delay is encountered each time a coil of wire is depleted. As a coil nears depletion, it is necessary in many operations to shut down the line for a relatively long period of time in order to prepare the line to handle the next coil. For example, a new coil must be loaded into place, its leading end and the trailing end of the preceding coil must be prepared for welding and then the two ends must be welded, annealed and de-flashed. Such operations usually take between 15 and 30 minutes to accomplish and, during that time, the production machine must remain idle. In some cases, a coil only lasts 40 minutes and thus the production machine is idle a substantial percentage of the time. With the advent of faster, more sophisticated and more expensive production machines, the down time which occurs during coil changeover has become a far more critical factor than was the case in the past.